共查询到20条相似文献,搜索用时 15 毫秒
1.
L. Gremillard L. Martin L. Zych E. Crosnier J. Chevalier A. Charbouillot P. Sainsot J. Espinouse J.-L. Aurelle 《Acta biomaterialia》2013,9(7):7545-7555
The degradation of zirconia-based ceramic components for total hip arthroplasty (head and cup) has been the topic of many works. However, the correlation between what is measured in vivo and what is expected from in vitro simulations on hip simulators may be sometimes feeble, especially where zirconia component are concerned, mainly due to a lack of representativeness of in vitro experiments. The present study seeks to explore the combined effects of hydrothermal ageing and wear on zirconia components. It shows that hydrothermal ageing increases the roughness of zirconia components, which in turn might increase the wear rate of the polyethylene counterparts. Moreover, the friction during hip simulation increases the ageing rate of the zirconia components. This auto-accelerating degradation may explain some of the poor long-term in vivo results of zirconia hip prostheses reported in the literature. Finally, it is shown that zirconia-toughened alumina components may be free from this combined degradation. 相似文献
2.
Morita Y Nakata K Kim YH Sekino T Niihara K Ikeuchi K 《Bio-medical materials and engineering》2004,14(3):263-270
While only alumina is applied to all-ceramic joint prostheses at present, a stronger ceramic is required to prevent fracture and chipping due to impingement and stress concentration. Zirconia could be a potential substitute for alumina because it has high strength and fracture toughness. However, the wear of zirconia/zirconia combination is too high for clinical use. Although some investigations on composite ceramics revealed that mixing of different ceramics was able to improve the mechanical properties of ceramics, there are few reports about wear properties of composite ceramics for joint prosthesis. Since acetabular cup and femoral head of artificial hip joint are finished precisely, they indicate high geometric conformity. Therefore, wear test under flat contact was carried out with an end-face wear testing apparatus for four kinds of ceramics: alumina monolith, zirconia monolith, alumina-based composite ceramic, and zirconia based composite ceramic. Mean contact pressure was 10 MPa and sliding velocity was 40 mm/s. The wear test continued for 72 hours and total sliding distance was 10 km. After the test, the wear factor was calculated. Worn surfaces were observed with a scanning electron micrograph (SEM). The results of this wear test show that the wear factors of the both composite ceramics are similarly low and their mechanical properties are much better than those of the alumina monolith and the zirconia monolith. According to these results, it is predicted that joint prostheses of the composite ceramics are safer against break down and have longer lifetime compared with alumina/alumina joint prostheses. 相似文献
3.
Takahashi Y Zhu W Sugano N Pezzotti G 《Journal of the Mechanical Behavior of Biomedical Materials》2011,4(7):993-1003
We have visualized at the nanometer scale the topological, chemical and mechanical characteristics of long-term in vivo exposed bearing surfaces of femoral heads made of monolithic alumina. Four self-mated alumina retrievals were studied, which were exposed in the human body for relatively long periods of time ranging between 7.7 and 10.7 yrs. Besides conventional morphological features, monitored by atomic force microscopy, the topographic distributions of point defects and lattice strain on the surface of the heads were systematically probed by collecting high spatially and spectrally resolved cathodoluminescence spectra from zones of different wear severity. Three types of optically active point-defect site could be detected: (i) oxygen vacancies; (ii) substitutional (aliovalent) cations; and, (iii) interstitial aluminum cations. These luminescent sites represent the main defects progressively developed in the alumina lattice during exposure in human hip joints. A clear evolution toward (environmentally driven) off-stoichiometry was found with progressing wear. Moreover, the shallow electro-stimulated optical probe also detailed the presence of lattice strain fields (of both elastic and plastic nature) stored in the very neighborhood of the bearing surface. The present spectroscopic characterizations enable substantiating important tribochemical interactions between bearing surfaces and in vivo environment as pivotal parts of progressive events of wear degradation. 相似文献
4.
《Acta biomaterialia》2014,10(8):3756-3761
Porcelain fused to zirconia (PFZ) restorations are widely used in prosthetic dentistry. However, their susceptibility to fracture remains a practical problem. The failure of PFZ prostheses often involves crack initiation and growth in the porcelain, which may be followed by fracture along the porcelain/zirconia (P/Z) interface. In this work, we characterized the process of fracture in two PFZ systems, as well as a newly developed graded glass-zirconia structure with emphases placed on resistance to interfacial cracking. Thin porcelain layers were fused onto Y-TZP plates with or without the presence of a glass binder. The specimens were loaded in a four-point-bending fixture with the thin porcelain veneer in tension, simulating the lower portion of the connectors and marginal areas of a fixed dental prosthesis (FDP) during occlusal loading. The evolution of damage was observed by a video camera. The fracture was characterized by unstable growth of cracks perpendicular to the P/Z interface (channel cracks) in the porcelain layer, which was followed by stable cracking along the P/Z interface. The interfacial fracture energy GC was determined by a finite-element analysis taking into account stress-shielding effects due to the presence of adjacent channel cracks. The resulting GC was considerably less than commonly reported values for similar systems. Fracture in the graded Y-TZP samples occurred via a single channel crack at a much greater stress than for PFZ. No delamination between the residual glass layer and graded zirconia occurred in any of the tests. Combined with its enhanced resistance to edge chipping and good esthetic quality, graded Y-TZP emerges as a viable material concept for dental restorations. 相似文献
5.
"Neurocompatibility" is a broad definition which comprises aspects of biocompatibility, chemical and physical surface properties, and biostability of an artificial substrate interfaced with a neural tissue. The main issue coming from the analysis of the state of art of neuroprosthesis and neuron/electrode interfaces is the strong influence of electrode surface morphology on neurocompatibility. Enhanced functions of neurons have been observed on nano-structured materials. This paper proposes the use of focused ion beam (FIB) technology as high precision machining technique to modify the surface morphology of an interface material. By controlling the ion milling in three dimensions, the fabrication of a surface with any predefined morphology becomes possible with nanometric precision. In vitro tests on PC12 cells cultured on surfaces with different morphologies show that the surface morphology influences the cell adhesion. Experimental results suggest an enhancement of the interaction between cells and artificial surfaces at a specific scale (tens of nanometres) which is the typical scale of cellular interaction in the extra-cellular matrix (ECM) of living organisms. 相似文献
6.
Synthesis and characterization of collagen/hyaluronan/chitosan composite sponges for potential biomedical applications 总被引:2,自引:0,他引:2
Yen-Chih Lin Fa-jui Tan Kacey G. Marra Shyh-Shyan Jan Deng-Cheng Liu 《Acta biomaterialia》2009,5(7):2591-2600
Cells, scaffolds and growth factors are three main components of a tissue-engineered construct. Collagen type I, a major protein of the extracellular matrix (ECM) in mammals, is a suitable scaffold material for regeneration. Another important constituent of the ECM, hyaluronic acid (hyaluronan, HA), has been used for medical purposes due to its hydrogel properties and biodegradability. Chitosan is a linear polysaccharide comprised of β1- to β4-linked d-glucosamine residues, and its potential as a biomaterial is based on its cationic nature and high charge density in solution. This study was conducted to evaluate the characteristics of scaffolds composed of different ratios of type I comb collagen and chitosan with added HA in order to obtain the optimum conditions for the manufacture of collagen–hyaluronan–chitosan (Col–HA–Ch; comprising collagen, HA and chitosan mixed in different ratios: 10:1:0, Col10HACh0; 9:1:1, Col9HACh1; 8:1:2, Col8HACh2; 7:1:3, Col7HACh3; 6:1:4, Col6HACh4; and 5:1:5, Col5HACh5) composite porous scaffolds. Microstructural observation of the composite scaffolds was performed using scanning electron microscopy. The mean pore diameters ranged from 120 to 182 μm and decreased as the chitosan composition increased. All scaffolds showed high pore interconnectivity. Swelling ratio measurements showed that all specimens could bind 35- to 40-fold of physiological fluid and still maintain their form and stability. For tensile strength, the optimal ratio of collagen and chitosan was 9:1. Thermal stability was investigated using a differential scanning calorimeter and showed that Col5HACh5 and Col6HACh4 were significantly more stable than the other groups. In enzymatic sensitivity, a steady increase in the biostability of the scaffolds was achieved as the chitosan concentration was increased. In biocompatibility testing, the proliferation of the fibroblasts cultured in Co-HA-Ch tri-copolymer scaffolds was high. Overall, we observed the 9:1:1 mixing ratio of collagen, hyaluronan and chitosan to be optimal for the manufacture of complex scaffolds. Furthermore, Col–HA–Ch tri-polymer scaffolds, especially Col9HACh1, could be developed as a suitable scaffold material for tissue engineering applications. 相似文献
7.
Qin Zou Bin Cai Junfeng Li Jidong Li 《Journal of biomaterials science. Polymer edition》2017,28(7):601-615
We have developed tourmaline/chitosan (Tur/CS) composite films for wound healing applications. The characteristics of composite films were studied by optical microscope, infrared spectra and X-ray diffraction. Tur particles were uniformly distributed in the CS film and the crystal structure of CS was not remarkably changed except the decrease of crystallinity. The influence of Tur on wound healing applications was characterized by modulating Tur concentrations in the Tur/CS composite film prepared by loading Tur powder into CS matrix with different proportion (0, 1/40 and 1/10). Then L929 cells were co-cultured on the composite films to access the cytotoxicity in vitro. Tur concentrations strongly influenced cell process extension. Tur/CS composite film with 1/40 mass ratio could promote the cell adhesion and proliferation. Fewer and shorter processes were observed at high Tur density. When the composite films were transplanted on porcine full-thickness burn wounds, histological results demonstrated that the Tur/CS group with 1/40 mass ratio had a significantly higher number of newly-formed and mature blood vessels, and fastest regeneration of dermis. Based on the observed facts these films can be tailored for their potential utilization in wound healing and skin tissue engineering applications. 相似文献
8.
Background
Prior knee surgery and arthroscopy is known to increase complications and re-operations in subsequent total knee arthroplasty (TKA). We set out to examine the time dependant effect of arthroscopy on Patient Reported Outcome Measures following subsequent TKA.Methods
A retrospective review of theatre and clinical records identified 186 patients who underwent TKA within a year of arthroscopy (2009–2013). Oxford knee score (OKS) data was compared with a published cohort from the same department (1708 patients).Results
One hundred and eighty six patients were identified who underwent TKA within a year of arthroscopy; 112 females, 74 males; mean age 64 (SD 10); mean BMI 31.4 (SD 4.6). There was no significant difference between groups with respect to sex, age, BMI, or pre-operative OKS.One hundred and three patients underwent TKA within six months of arthroscopy. This group had a significant reduction in OKS compared to the previously published cohort (32.8 vs 36.3, p < 0.005). There was no significant difference in OKS when TKA was performed more than six months after arthroscopy (35.3).The re-operation rate was 14% in the arthroscopy group, with a revision rate of 3.8% vs 1.6% in a previously published large cohort from the same institution.Conclusions
There appears to be a negative impact of arthroscopy in relation to subsequent TKA which seems to be time dependent. TKA should not routinely be performed within six months of arthroscopy. This should inform guidelines on the management knee osteoarthritis. 相似文献9.
Jodi A. Lindsay 《International journal of medical microbiology : IJMM》2014,304(2):103-109
Whole genome sequencing and microarrays have revealed the population structure of Staphylococcus aureus, and identified epidemiological shifts, transmission routes, and adaptation of major clones. S. aureus genomes are highly diverse. This is partly due to a population structure of conserved lineages, each with unique combinations of genes encoding surface proteins, regulators, immune evasion and virulence pathways. Even more variable are the mobile genetic elements (MGE), which encode key proteins for antibiotic resistance, virulence and host-adaptation. MGEs can transfer at high frequency between isolates of the same lineage by horizontal gene transfer (HGT). There is increasing evidence that HGT is key to bacterial adaptation and success. Recent studies have shed light on new mechanisms of DNA transfer such as transformation, the identification of receptors for transduction, on integration of DNA pathways, mechanisms blocking transfer including CRISPR and new restriction systems, strategies for evasion of restriction barriers, as well as factors influencing MGE selection and stability. These studies have also lead to new tools enabling construction of genetically modified clinical S. aureus isolates. This review will focus on HGT mechanisms and their importance in shaping the evolution of new clones adapted to antibiotic resistance, healthcare, communities and livestock. 相似文献
10.
Julie K. Cremeans-Smith Jessica M. Boarts Kenneth Greene Douglas L. Delahanty 《Journal of behavioral medicine》2009,32(3):223-233
The present study examines the reasons cited by 103 patients for their electing to undergo total knee arthroplastic surgery
and the relationship between these reasons and their post-operative pain and range of motion. Results suggest that individuals
who describe different reasons for undergoing surgery vary in their post-operative recovery. Specifically, patients who cite
pain as the reason they are undergoing surgery report greater levels of pain during the early post-operative period. In contrast,
patients who describe goals of regaining mobility or a specific activity as their reason for undergoing surgery achieve a
greater range of motion during early post-operative physical therapy. Individuals who express avoidance goals for undergoing
total knee arthroplasty report more severe post-operative pain at 1 and 3 months following surgery compared to patients who
express approach goals. Interventions targeted towards patients reporting pre-operative pain or avoidance goals may decrease
subsequent post-operative pain and increase mobility. 相似文献
11.
Jung YS Jeong JH Yook S Im BH Seo J Hong SW Park JB Yang VC Lee DY Byun Y 《Biomaterials》2012,33(1):295-303
This study proposes a combination method of using 3,4-dihydorxy-l-phenylalanine (DOPA) conjugated heparin (heparin-DOPA) and a low dose of anti-CD154 monoclonal antibody (MR-1) treatment to improve the survival time of intrahepatic islet xenograft. To inhibit instant blood mediated inflammatory reactions, heparin-DOPA was directly grafted to the pancreatic islet surface. The surface coverage of heparin-DOPA, the viability and functionality of heparin-DOPA grafted islets were evaluated. In addition, the combined effect of grafted heparin-DOPA and a low dose of MR-1 (a T-cell targeting immunosuppressive drug) on the survival of islet was evaluated in a xenograft model. Both unmodified islets and heparin-DOPA grafted islets were completely rejected within 2 weeks after intraportal transplantation. However, when 0.1 mg/mouse of MR-1 was administered (at day 0, 2, 4, 6 of transplantation) to 11 mice that had heparin-DOPA grafted islets transplanted to, seven out of the recipients maintained normoglycemia over 60 days. Therefore, we propose that a developed combinatory immunoprotection protocol of surface modification of pancreatic islets using heparin-DOPA with a low dose of MR-1 can be effective in prolonging the survival rate of transplanted islets in a xenograft model. 相似文献
12.
Biological performance of a new beta-TCP/PLLA composite material for applications in spine surgery: in vitro and in vivo studies 总被引:3,自引:0,他引:3
Aunoble S Clément D Frayssinet P Harmand MF Le Huec JC 《Journal of biomedical materials research. Part A》2006,78(2):416-422
The objective of this research was to carry out an in vitro and in vivo study of the biological performance of PLLA/beta-TCP composite materials, to estimate the scope of their potential applications in bone surgery. Samples with increasing beta-TCP (0-60% w/w) contents were processed by injection molding. The in vitro study consisted of an evaluation of inflammatory potential by assaying the IL-1alpha secreted by monocytes, and then cell proliferation (counting) and phenotype expression (PAL and I collagen) in human osteogenous cells. The in vivo study was carried out using cylindrical implants of composite materials composed of composite materials containing 0 or 60% beta-TCP and pure beta-TCP, respectively. The implants were inserted in femoral sites in rabbits, using the Kathagen protocol. Each animal received a 60% implant, with either a 0 or a 100% implant in the contralateral femur, so that the materials could be compared with one another. Five animals were examined for each material and implantation period, giving a total of 30 animals. This study showed that adding increasing percentages of beta-TCP to a lactic acid polymer matrix stimulated the proliferation of human osteogenous cells and synthesis of the extracellular bone matrix in a dose-dependent manner. In vivo results indicate that, in comparison with pure PLA, tricalcium phosphate-containing composite materials had faster degradation kinetics, caused less inflammatory reaction, and promoted contact osteogenesis. The composite material containing 60% beta-TCP demonstrated a similar performance to pure tricalcium phosphate bone grafts in terms of osteogenesis, and is apparently compatible with the production of intra-osseous implants for situations representing high levels of mechanical strain. 相似文献
13.
Lyerly WH 《TB & HIV》1996,(11):10-11
Unlike most infectious diseases in Africa, HIV/AIDS affects the urban elite as well as the rural poor, and generally during their most economically productive years. An increase in deaths among young adults of the magnitude predicted is likely to have substantial adverse effects on economic, political, and military/security stability throughout Africa. AIDS is causing increased stress on fragile African economic infrastructures as labor productivity declines, particularly in agricultural, labor-dependent economies. AIDS is causing obstacles to trade, foreign investment and tourism. Health systems and social coping mechanisms already are overburdened. High rates of HIV infection among police and military personnel threaten internal security. Furthermore, the demobilization of military forces in Africa may exacerbate the epidemic when HIV-infected soldiers return home and spread the virus. This presentation will illustrate why African AIDS Programs must be expanded to mitigate the multisectoral impact of the epidemic while preserving its spread. 相似文献
14.
A common surgical goal in TKA is to restore neutral alignment of the lower limb by making bone cuts perpendicular to the mechanical axes of the femur and tibia. Standard practice for many surgeons is to use the same distal femoral valgus resection angle for all patients, assuming little or no variation in the femoral mechanical-anatomical (FMA) angle between different patients' knees. This study analysed 174 pre-operative hip-knee-ankle radiographs of osteoarthritic knees (157 patients, 87 female and 70 male, mean age 70years and mean BMI 31.8). Measurements of mechanical femorotibial (MFT) and FMA angles were made. The mean FMA angle was 5.7° (SD 1.2°, range 2° to 9°). There was a statistically significant difference between the FMA angle for males and females with males tending to have larger FMA angles (p<0.001). There was a statistically significant correlation between MFT and FMA angle (r=-0.499) with varus knees tending to have larger FMA angles (p<0.001). These results indicate a wide distribution of FMA angle in an osteoarthritic population. In terms of achieving appropriate coronal alignment in TKA the use of a fixed valgus resection angle is not suitable for all patients and it may be preferable to adjust the distal femoral cut according to individual FMA angles. However if this angle is not available the cut may be adjusted according to pre-operative coronal alignment, using 6° for neutral/mild varus, >6° for more severe varus and <6° for valgus knees. 相似文献
15.
16.
Kersemaekers AM Honecker F Stoop H Cools M Molier M Wolffenbuttel K Bokemeyer C Li Y Lau YF Oosterhuis JW Looijenga LH 《Human pathology》2005,36(5):512-521
Carcinoma in situ (CIS) is the precursor of malignant testicular germ cell tumors (GCTs) of adolescents and young adults, being the neoplastic counterpart of primordial germ cells/gonocytes. Carcinoma in situ cells will develop into invasive seminoma/nonseminoma. Gonadoblastoma (GB) is the precursor of invasive GCTs in dysgenetic gonads, predominantly dysgerminoma (DG). In this process, part of the Y chromosome (GBY region) is involved, for which TSPY is a candidate gene. A detailed immunohistochemical survey was performed for the known diagnostic markers, germ cell/placental alkaline phosphatase (PLAP), c-KIT, and OCT3/4, as well as testis-specific protein on the Y chromosome (TSPY) on a series of GBs, and adjacent invasive DGs. All 5 patients were XY individuals (4 females and 1 male). In contrast to c-KIT, PLAP was positive in all cases. The immature germ cells of GBs were positive for OCT3/4, whereas the mature germ cells were negative for this marker, but positive for TSPY. In every GB, a minor population of germ cells positive for both markers could be identified, similar to most CIS cells and early invasive DG. On progression to an invasive tumor, TSPY can be lost, a process that is also detectable in invasive testicular GCTs compared to CIS. These results indicate that GB is a heterogeneous mix of germ cells, in which the OCT3/4-positive cells have the potential to undergo progression to an invasive tumor. These early invasive stages are initially also positive for TSPY (like CIS), supporting a positive selection mechanism. Therefore, OCT3/4 in combination with TSPY is valuable to identify malignant germ cells in dysgenetic gonads. This could allow better prediction of the risk of progression to a GCT. In addition, the data support the model that GB represents the earliest accessible developmental stage of malignant GCTs. 相似文献
17.
Liliana Basabe Nelson Cabrera Vladimir Yong Javier Menéndez Julio M. Delgado L. Rodríguez 《Current genetics》1996,30(1):89-92
A method to obtain K. marxianus mutants has been developed. Different auxotrophic mutants were isolated by nystatin and snail-enzyme enrichment procedures
using an incubation time of 2 h before adding the antibiotic or the enzyme respectively. All his mutants analyzed by complementation tests turned out to belong to the same complementation group. Some of them were transformed
and complemented by the S. cerevisiae HIS3 gene. These non-reverting his3 mutants contain no heterologous sequence, which is essential to make them acceptable for application in the food industry.
Received: 15 November/21 December 1995 相似文献
18.
Aliyeh Ghamkhari Bakhshali Massoumi Roya Salehi 《Journal of biomaterials science. Polymer edition》2017,28(17):1985-2005
In this work, a novel thermo-responsive Fe3O4/poly(methylmethacrylate-b-N-isopropylacrylamide-b-acrylic acid) magnetic composite nanosphere was synthesized for anticancer drug delivery applications. For this propose, the poly(methylmethacrylate-b-N-isopropylacrylamide-b-acrylic acid) [poly (MMA-b-NIPAAm-b-AAc)] was synthesized via reversible addition-fragmentation transfer method. The physic-chemical characterization of the Fe3O4/poly(MMA-b-NIPAAm-b-AAc) magnetic composite nanosphere was investigated by FTIR, HNMR spectroscopies and GPC, FESEM, XRD, VSM and DLS. The thermo-sensitivity of the Fe3O4/P(MMA-b-NIPAAm-b-AAc) magnetic composite nanosphere was confirmed via DLS at 40 °C. DOX encapsulation efficiency was calculated to be 98.2%. The effect of temperature and pH on release behaviors of stimuli responsive DOX-loaded Fe3O4/P(MMA-b-NIPAAm-b-AAc)] magnetic composite nanosphere were investigated. The release rate at pH 7.4, 5.4 and 4 (T = 37 °C) was reached about 24.4, 42.4 and 57.5 wt%, after 4–5 day. The release rate improved at tumor simulated environment (t:40 °C and pH ≤ 5.4). The cytotoxic effects of the magnetic composite nanosphere were appraised by MTT assay and the results indicated that novel developed smart nanocomposite here was nontoxic to MCF-7 cells and can be applied as anti-cancer drug delivery system. Also, the results of the Cellular uptake of MCF7 cells treated with rhodamine labeled DOX-loaded nanocarrier for 2 h have indicated that DOX can be applied as cytotoxic agent and targeting ligand. 相似文献
19.
Individual characteristics of prednisolone and cortisol pharmacokinetics in five young healthy subjects administered prednisolone
in a single oral dose of 25 mg are described. The results suggests that prednisolone inhibits the glucocorticoid function
of the adrenal cortex. It is concluded that the pharmacokinetics of prednisolone can be assessed from the reductions in serum
cortisol concentration which it causes.
Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 122, No. 7, pp. 51–54, July, 1996 相似文献
20.
Bertato MP Oliveira CP Wajchenberg BL Lerario AC Maranhão RC 《Clinics (S?o Paulo, Brazil)》2012,67(4):347-353